Thanks all. By the time we got to Tower Bridge we'd done a lot of walking so didn't want to stray as far as, say, Brick Lane etc. We had a quick look around the Tower area & St Katharine's Dock to see what was about, and thought about the closer recommendations such as the Empress, but I'd had another look that morning and found Wilton's do food 5pm to 9pm and Thursday night was pizza night, so we had a really good pizza and a garlic and herb flatbread; plenty for two for £13, great service and convivial surroundings.
Thanks to everyone for their input.